1. Field of the Invention
The present invention relates to an image processing apparatus and method for reading and recording an image, for example, by using a color expression known as "c-RGB" (colorimetric RGB).
2. Description of the Related Art
A newly developed method of expressing colors involves obtaining the apex of a triangle substantially circumscribed on the spectrum locus of a chromaticity diagram, and expressing color by a combination of reference color stimulus data indicated by this apex. This method shall be referred to as "c-RGB" hereinafter.
In a case where this method is applied to an apparatus for reading a color film, however, the color of a subject in photography cannot be reflected correctly for reasons such as a disruption in the color balance on the film due to the influence of the light source, etc., at the time of photography.
Further, in such a conventional color image processing apparatus, calibration is made in a signal form (RGB or YMCK) which is inherent to a color image reading unit or a color image recording unit. The calibration represents that a reading unit is corrected so that the signal obtained when a color of known color characteristics is read in the reading unit becomes an expected signal, and that a recording unit is corrected so that the color obtained when a predetermined signal is output to an image recording unit becomes an expected color.
However, the above color image processing apparatus has the problem that since calibration is made in a signal form inherent to the apparatus, when the reading unit and recording unit are replaced by another reading unit and recording unit, respectively, the color characteristics change.
In addition, if calibration is made for known NTSC (National Television System Committee) RGB signals, NTSC correction must be made by raising to 0.45 th power, and the operation is thus made troublesome. There is also the problem that since the range of colors which can be expressed is limited, the color reproducible range of all reading units and recording units cannot be expressed.